1. Field of the Invention
This invention relates to wood-polymer composites. In one aspect, this invention relates to wood-polymer composites comprising a wood substrate impregnated with a dicyclopentenyl acrylate or methacrylate polymer. In another aspect, this invention relates to processes for preparing said wood-polymer composites comprising impregnating a wood substrate with a liquid dicyclopentenyl acrylate or methacrylate monomer and curing the resulting monomer-impregnated wood substrate.
2. Description of the Prior Art
Various wood-polymer composites are known in the art. For example, U.S. Pat. Nos. 3,560,255 and 3,790,401, both by Maine, teach a wood-polymer composite consisting essentially of wood impregnated with a thermoplastic polymer of tert-butylstyrene. Whereas tert-butylstyrene monomer is amenable to a heat-catalyst cure, i.e. a heat cure in the presence of a thermal initiator, it is not compatible with a high-energy radiation cure, such as .gamma.-rays. Moreover, tert-butylstyrene polymer is relatively soft and readily attacked by hydrocarbons.
U.S. Pat. Nos. 3,077,417-20 by Kenaga teach a wood-polymer composite comprising a wood substrate impregnated with a polymer derived from a vinyl monomer, such as methyl methacrylate. A .gamma.-radiation cure is used because the volatility of methyl methacrylate precludes both the efficient production of thin-section products, such as veneer, and the use of a heat-catalyst cure. Moreover, the monomer-impregnated wood substrate shrinks on cure which can thereby cause warping or internal checking in heavy members.
U.S. Pat. No. 3,627,659 by Marx et al. teaches a process for the production of coatings, impregnations or bonding agents by polymerization and cross-linking of mixtures containing olefinically unsaturated esters containing halogen by means of ionizing radiation. Therein, a mixture (by weight) of 80 parts 3a,4,5,6,7,7a-hexahydro-4,7-methanoindenyl acrylate-(5) (i.e. dicyclopentenyl acrylate), 10 parts 2,3-dichloro-3-bromoacrylic acid-(1) and 10 parts 2-chloroallyl acrylate is drawn into a film onto a plywood board and irradiated with an electron beam. Marx et al. do not teach impregnating with said mixture and the presence of the halogen-containing, olefinically unsaturated ester is critical to the teaching.